%0 Journal Article %1 Sperryetal_06 %A Sperry, J. S. %A Hacke, U. G. %A Pittermann, J. %D 2006 %J American Journal of Botany %K bibtex-import, citeulikeExport diameter, hydraulics, theory, unread %P 1490--1500 %T Size and function in conifer tracheids and angiosperm vessels %V 93 %X The wide size range of conifer tracheids and angiosperm vessels has important consequences for function. In both conduit types, bigger is better for conducting efficiency. The gain in efficiency with size is maximized by the control of conduit shape, which balances end-wall and lumen resistances. Although vessels are an order of magnitude longer than tracheids of the same diameter, they are not necessarily more efficient because they lack the low end-wall resistance of tracheids with torus-margo pits. Instead, vessels gain conducting efficiency over tracheids by achieving wider maximum diameters. End-walls contributed 56 64\% to total xylem resistance in both conduit types, indicating that length limits conducting efficiency. Tracheid dimensions may be more limited by unicellularity and the need to supply strength to homoxylous wood than by the need to protect against cavitation. In contrast, the greater size of the multicellular vessel is facilitated by fibers that strengthen heteroxylous wood. Vessel dimensions may be most limited by the need to restrict intervessel pitting and cavitation by air-seeding. Stressful habitats that promote narrow vessels should favor coexistence of conifers and angiosperms. The evolution of vessels in angiosperm wood may have required early angiosperms to survive a phase of mechanic and hydraulic instability.

@article{Sperryetal_06, abstract = {{The wide size range of conifer tracheids and angiosperm vessels has important consequences for function. In both conduit types, bigger is better for conducting efficiency. The gain in efficiency with size is maximized by the control of conduit shape, which balances end-wall and lumen resistances. Although vessels are an order of magnitude longer than tracheids of the same diameter, they are not necessarily more efficient because they lack the low end-wall resistance of tracheids with torus-margo pits. Instead, vessels gain conducting efficiency over tracheids by achieving wider maximum diameters. End-walls contributed 56 64\% to total xylem resistance in both conduit types, indicating that length limits conducting efficiency. Tracheid dimensions may be more limited by unicellularity and the need to supply strength to homoxylous wood than by the need to protect against cavitation. In contrast, the greater size of the multicellular vessel is facilitated by fibers that strengthen heteroxylous wood. Vessel dimensions may be most limited by the need to restrict intervessel pitting and cavitation by air-seeding. Stressful habitats that promote narrow vessels should favor coexistence of conifers and angiosperms. The evolution of vessels in angiosperm wood may have required early angiosperms to survive a phase of mechanic and hydraulic instability.}}, added-at = {2019-03-31T01:14:40.000+0100}, author = {Sperry, J. S. and Hacke, U. G. and Pittermann, J.}, biburl = {https://www.bibsonomy.org/bibtex/29fc03446b694c5578cf1ed4f495d3391/dianella}, citeulike-article-id = {1524058}, comment = {(private-note)In theory, a conduit of a given diameter could become long enough to virtually eliminate the contribution of the end-walls to its conductivity. At this saturating length the conduits conductivity would equal its HagenPoiseuille lumen conductivity (Sperry and Hacke, 2004). In practice, no conifer tracheid or angiosperm vessel in Fig. 1 approached this saturating length. End-walls accounted for 64 6 4\% of the total resistivity in tracheids and 56 6 2\% in vessels (mean 6 SE). Such a large end-wall limitation implies that conduit length is constrained in tracheids as well as in vessels. Apparently, the angiosperms evolved longer conduits instead of sophisticated pits like conifers. HAVE READ TO PAGE 1495}, interhash = {ee648ad25f02bb0162f8802936ba9a36}, intrahash = {9fc03446b694c5578cf1ed4f495d3391}, journal = {American Journal of Botany}, keywords = {bibtex-import, citeulikeExport diameter, hydraulics, theory, unread}, pages = {1490--1500}, posted-at = {2007-07-31 07:05:32}, priority = {5}, timestamp = {2019-03-31T01:16:26.000+0100}, title = {{Size and function in conifer tracheids and angiosperm vessels}}, volume = 93, year = 2006 }